1. Field of the Invention
This invention relates to a push button switch assembly and, more particularly, to a constituent portion of the push button switch assembly by which a knob and a push button switch are connected to each other.
2. Description of the Prior Art
Generally in an electronic apparatus such as a radio receiver which is operated by push button control elements, it is desirable that the push button switch is securely operated, and that the operation occurs smoothly without malfunction. The push button switch is mounted typically on a chassis through a printed board. An operating rod of the push button switch is fitted into a hole made in the end surface of the knob and the knob is guided by an escutcheon fixed within an opening of the front panel of the receiver. Since there is some error in the forming accuracy, working accuracy and assembling accuracy of the chassis, printed board and the panel, there is the possibility that the hole of the knob is deflected from the operating rod of the push button switch. In that case, when the operating rod is forcibly inserted into the hole of the knob, the knob and the escutcheon chafe against each other when the knob is pushed. Moreover, there is the possibility that the knob, when pushed again to release the selected operation, may not move back to the original position on releasing.
A push button switch assembly has been proposed which obviates the above-described disadvantage but not without eliminating certain other undesirable attributes. Such prior art push button assembly is illustrated in FIG. 1 and will be described in more detail to provide a better understanding and background to appreciate the push button assembly of the present invention.
As shown in FIG. 1, the prior art push button assembly 1 includes a depressible push button member or knob 2 slidably disposed and guided within an opening 3 of an escutcheon member 4 which is in turn mounted within an opening 5 within the front panel 6 of the electronic device such as a receiver (not shown). Knob 2 includes a flanged portion 7 disposed on the interior facing side of the knob which bears against the surface of escutcheon 4 to limit outward movement of the knob. The assembly also includes a push button switch 8 mounted on a printed circuit board 9 within the cabinet of the electronic device. Push button switch 8 includes an operating rod 10 extending therefrom which has its free end 11 in contact with flange 7 of knob 2. Operating rod 10 is urged to remain in contact with knob 2 by a coil spring 12 which has one end disposed against a flange 13 extending from rod 10 and its other end against a flange 14 on the housing of push button switch 8.
When the knob 2 is depressed operating rod 10 moves against the spring action of spring 12 into the housing of the push button switch 8, by a predetermined length, and is retained. When knob 2 is again depressed operating rod 10 is projected back to its original position. In the push button switch assembly of the prior art shown in FIG. 1 no hole is provided for fitting the operating rod 10 in the end surface of the knob 2 and knob 2 is not fixed to operating rod 10. End 11 of operating rod 10 merely contacts flange 7 of knob 2. Accordingly, the contact position between the knob 2 and operating rod 10 may change in the direction normal to the pushing direction of the knob 2. Even when the central axis X of the knob 2 or that of the opening 3, as shown in FIG. 1, is deflected from the central axis Y of operating rod 10 by the length G, or even when the push button switch 8 is inclined from the horizontal position shown in FIG. 1, knob 2 can be pushed without trouble and knob 2 is not retarded in its movement by escutcheon 4. Thus, push button switch 8 can be operated through the operating rod 10 by the knob 2.
However, when panel 6 is removed from the electronic device during disassembly, for example to repair the device, there is the possibility that knob 2 may fall from the escutcheon 4 into the cabinet. If knob 2 is made of metal, there is the possibility that it may short-circuit one or more of the circuit elements of the printed circuit board 9 causing more damage to the apparatus. Accordingly, much care must be taken in disassembling the apparatus and handling of the apparatus for disassembly is made more troublesome.
To solve the above-described problem, a push-button switch assembly, shown in FIGS. 2 to 4 has been proposed. Parts in FIG. 2 to FIG. 4 which correspond to those in FIG. 1, are denoted by the same reference numerals and further description of these parts will be omitted.
In the prior art push button assembly shown in FIGS. 2 to 4 the operating rod 10 of push button switch 8 is fitted to a combining member 20, shown in FIG. 3, which comprises a square cylindrical segment 20b having a square shaped penetrating hole 20a and a pair of opposed support plates 20c fixed to the side wall of the cylindrical segment 20b. The combining member 20 is inserted into a cap-like knob 22, FIG. 4, which includes an interior recess 24, a pair of opposed cutouts 25 and a pair of holding arms 23 formed by each cutout 25. Each of the cutouts 25 comprises a slit 25a extending along the periphery of knob 22 and a contiguous opening 25b extending toward the open end.
The above described parts are assembled in the manner shown in FIG. 2. The operating rod 10 of the push button switch 8 is fitted into the penetrating hole 20a of the combining member 20, and support plates 20c of the combining member 20 are inserted into the slits 25a of knob 22. An engaging groove 10a is formed in operating rod 10 to engage with a projection 20d formed in the inner wall of combining member 20.
The cylindrical part 20b of combining member 20, to which operating rod 10 of push button switch 8 is fitted, is inserted into recess 24 of knob 22 so that support plates 20c are placed at openings 25b. Knob 22 is then rotated in the direction shown by arrow A in FIG. 4.
However, while this type assembly obviates the problem of losing a knob during disassembly of the apparatus this knob assembling operation is troublesome. When the width of slits 25a are nearly equal to the thickness of support plates 20c, or the slits are slightly smaller than the plates, to firmly hold support plates 20c, the support plates 20c must be forcibly inserted into slits 25a. If the support plates 20c are formed of a weak material, there is the possibility that they will break off during assembly. If push button switch 8 is mounted on a slant on printed circuit board 9, knob 22 may be caught by the escutcheon 4 since knob 22 is firmly coupled with combining member 20. Thus push button switch 8 cannot be operated smoothly in such a situation.
When the width of slits 25a are made larger than the thickness of support plates 20c, to avoid the above-described disadvantage, as shown in FIG. 2, knob 22 cannot be securely held and the knob 22 is apt to move about to make for sloppy operation and to vibrate during use which may add an undesirable vibrating noise.